Disposable aerosol spray cans have become very popular due to the convenience of being able to spray a wide array of fluid materials upon a surface. Billions of aerosol cans are consumed and discarded each year worldwide. However, there is a large price we pay ecologically for this convenience.
Graffiti, for example, is commonly done with aerosol cans, to the extent they are banned or controlled in some jurisdictions.
Aerosol cans release propellant gases into the atmosphere that are believed to add to the "greenhouse effect". And, non-fluorocarbon propellants, which are better than CFC's ecologically, are generally flammable and may injure people who breath the discharged gas in a closed area or get burned in a flash fire. Flammable conditions always exist when propane is used as the propellant. Some governmental agencies have limited the types and amounts of propellant gases that may be used in disposable aerosol spray cans.
Another problem is that current aerosol spray cans are disposable after only one use and are not refillable, creating tons of non-recyclable waste. If aerosol cans were recyclable or refillable, the waste factor would be reduced.
There are also problems of safe and user friendly discharge of some fluids using aerosol cans. For example, standard aerosol cans discharge abruptly when used with fluids containing particulate matter in suspension, for example. The maximum safe inflated pressure of the can is required to discharge heavy viscous fluids. Some fluid materials will not spray out of aerosols at all.
The Venturi spray effect that current disposable aerosol cans use is limited to liquids with a thin-enough viscosity to sustain this effect. However, atomization allows a broader range of viscous fluids and other liquid materials to be sprayed. Compressed air is injected just behind a spray orifice along with the fluid to achieve the atomization effect. Atomization is a preferred method of controlling the characteristics of the discharged spray.
Furthermore, some "settling" problems are not easily overcome by shaking aerosol cans with marbles or steel balls enclosed for that purpose. If the user had a way to open the can, complete mixing could be accomplished and confirmed.
It would be advantageous if there was an inexpensive substitution for the disposable aerosol spray can that is user refillable, that does not release propellant gases into the atmosphere, would spray a broader range of fluids, is not useful for graffiti vandals, is user-friendly with heavy viscous fluids, uses the atomization spray effect, and would allow the user to fully mix the contained materials.
U.S. Pat. No. 3,062,453 to Stem et al. (the '453 patent) discloses a traditional aerosol spray can utilizing an aerosol-pressurized texture material to spray the texture onto a wall or the like. The device described in the '453 patent has the disadvantages of the prior references, particularly in that it is not user refillable, and that it uses propellant gases to spray the texture material.
U.S. Pat. No. 4,948,054 (the '054 patent) issued to the present Applicant discloses an apparatus for spraying a texture material onto a wall or ceiling. Positive air pressure is created by closing an air escape opening on the apparatus with a finger, forcing the texture material downwards the apparatus and towards the exit orifice at the bottom of the apparatus. However, the apparatus disclosed in the '054 patent cannot be held upright in a spray can-like fashion, because the texture material is held in a large container positioned above the exit orifice, requiring the user to "hug" the apparatus with both arms during operation, thus not offering the ease of use and the portability found in traditional aerosol spray cans.